Marine storage structure



June 18, 1968 w. F. MANNING 3,388,556

MARINE STORAGE STRUCTURE Filed OC.. lO, 1966 22e FIG. l

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WILLIAM F. MANNING BY @MAQ 62W( ATTORNEY United States Patent O 3,388,556 MARINE STORAGE STRUCTURE William F. Manning, Dallas, Tex., assignor to Mobil Oil Corporation, a corporation of New York Filed Get. 10, 1966, Ser. No. 585,544 7 Claims. (Cl. 61--46.5)

ABSTRACT OF THE DISCLOSURE This specification and the accompanying drawings disclose an articulated marine storage structure capable of floating substantially horizontally on the surface of a body of water for towing purposes. When installed at a marine site, a storage section thereof is supported on the marine bottom and a pair of support sections, connected to the storage section on spaced, hinged, or pivotal axes, converge above the storage section. Piles are driven through legs, or caissons, of the support section to anchor the structure, and a deck is mounted over the converged support sections, over the storage section, at least near the surface of the body of water. The storage section is disclosed as a plurality of parallel tubes interconnected by intersecting tubular sections. Also illustrated and described is a specific method for installing the structure at a site by selective flooding of the various components thereof.

This invention relates to a storage structure that may be easily towed to a marine site, on the surface of a body of water and then submerged at the site, for fluid storage adjacent the bottom, and more particularly, to a submersible marine structure which can be anchored by piles driven from above the surface even in deep water and which has provision for a deck above the marine bottom, at least near the surface of the body of Water.

Present developments in the offshore oil and gas industry indicate that drillingand production efforts will be eX- tended to underwater areas, such as the outer fringes of the continental shelves and to the continental slopes (defined as areas where the water depth is over 600 feet and less than 6,000 feet), where submarine production systems are presently considered the most practical method of exploiting fluid mineral deposits located in the subaqueous formations, particularly where the underwater wellheads must be spaced far apart. Submerged, bottom-supported storage structures, able to accommodate at least ten days supply of accumulated fluid minerals, are an integral part of these submarine systems. Such a storage structure, while necessarily being large enough to accommodate the hydrocarbons that will be collected in a prolific enough field to be produced under the sea economically, must also be adapted to float on the surface of the body of water and be easily towed by tugs long distances from its port of embarkation to the marine site at which it is to be utilized. The term fluid minerals, for purposes of this discussion, is to be construed broadly and is intended to encompass minerals in slurries and other similar states of matter that maybe transported lup through a production passage of a well and/ or through iiowlines.

Furthermore, in a subsea production system, with the Wellheads, production satellites, gathering systems, and storage tanks, all being on the marine bottom, 600 feet or more below the surface, some means, in conjunction with the storage tanks, is necessary for transporting the accumulated fluid minerals from the depths to a tanker which periodically visits the area. As envisioned, such a system would necessarily include a surface, or near surface, station connected to a floating single point -mooring system for transporting the fluid minerals to a waiting tanker. However, there still remains the proble-ms that the depths for which Stich a submarine system is proposed would be too great for unsupported flexible lines to carry the fluid from the marine bottom to the surface; and that some means must be provided for locating the surface, or near surface station, without anchor lines which could break loose and become entangled with the subsea equipment, tearing the subsea equipment out as the surface station is driven by a storm.

One of the problems associated with a submerged storage structure is that of providing for rigid and positive anchoring of the storage structure due to the tremendous buoyancy of a very large tank when it is filled with lighterthan-water hydrocarbons. The anchoring means normally utilized with this type of structure includes jackets attached to the periphery of the structure through which piles are extended into the formations underlying the marine bottom, the piles being then grouted to the jackets. All of the known methods of driving a submerged pile in very deep water include a caisson for guiding the hammer. However, if long, rigid, upwardly extending caissons are rigidly attached to the storage structure prior to its being towed to an offshore location, the floating structure becomes dangerously top-heavy.

Accordingly, it is an aspect of the present invention to provide a submersible storage structure which can be easily towed on the surface of a body of water.

It is another aspect of the present invention to provide a submersible storage structure with articulated caisson means for driving piles therethrough from above the surface and for supporting a platform above t-he marine bottom, at least near the surface of the body of Water in which it is installed.

Other aspects and advantages of the present invention will be readily apparent from the following description, when taken in conjunction with accompanying drawings which illustrate useful embodiments in accordance with this invention, in which:

FIGURE 1 is a plan view of the marine storage structure of the present invention when under tow;

FIGURE 2 is an elevational View of the marine storage structure with the storage section thereof resting on the marine bottom and the articulated support sections being folded up to converge above the surface; and

FIGURE 3 is a schematic elevational View of the marine storage structure of the present invention illustrating a method for installing the structure on the marine bottom.

The invention comprises a marine storage structure having a storage section and at least a pair of opposed articulated support sections. The articulated support sections are so arranged that when the storage section rests on the marine bottom, the articulated support sections can be folded upward to converge at least near the surface of the body of water performing the dual function of caissons for driving piles into the bottom from above the surface for anchoring the storage section, and a support base for an upper deck section at least near the surface of the body of water. Moreover, when the structure is under tow the articulated support sections can lie fiat and float on the water surface along with the storage section.

Looking now to FGURE 1 of the drawings, the marine storage structure, generally designated 1t), consists of a uid storage section, in the form of la planar raft 12, and a pair of articulated support sections 14 and 16 connected to the raft 12 at opposite ends thereof. The pivotal axes of the articulated support sections Iare located within the raft itself as will be subsequently discussed. As `shown in FIGURE l the raft 12 is Welded up from a plurality of hollow storage tubes 18A-F held together, in parallel, by tubular spacer sections 20A-E and 22A-E forming a pair of perpendicularly intersecting spacer tubes. The storage tubes 13A-F can `be interiorly interconnected by the spacer `sections ZtlA-E and 22A-E to form substantially one enclosed storage area for the containment of liuids or each of the storage tubes 18A-E can be a contiguous tank, individually connected with production equipment and/or underwater wellheads and in fact each of the storage tubes 18A-E may be compartmented so that the rupture of :a single tube 18A--F would not necessarily require that the entire structure be brought back to the surface for repairs.

Each of the support sections 14 and 16 consists of a pair of hollow legs or caissons 24 converging at their outer ends and hinged or pivoted at spaced points at their inner ends between the outermost pairs of storage tubes 18A and 18B, and 18E and 18F, to connect the support sections 14 and 16 to the raft 12. The storage tubes 18B and 18E are slightly shorter than the overall length of the raft 12 to permit the angled legs 24 of the support sections 14 and 16 to fold out flat on the surface of the body of Water in the plane of the raft 12. The means for hinging or pivoting the legs 24 cannot simply be shafts extending through the legs 24 since it is necessary that .the legs 24 have unobstructed throughbores so that piles 30 can be driven therethrough. One possible method of fabricating articulated joints is by welding short shaft sections 26 and 28 coaxially to the inner and outer face of each of the legs 24 and journaling the shaft sections in bushings fixed to the opposing faces of the tubes 18A and 18B, and 18E and 18F, at each end of the raft 12.

Prior to towing the marine storage structure 10, a pile 30 is inserted in each leg 24, after which the legs 24 are capped to maintain buoyancy of the support sections 14 and 16. To prevent shifting of the piles 30 during towing, they are tack-welded in place in the inner ends of the respective legs 24. The iirst strike of a pile-driving hammer will break the weld and release the pile 30, the lower cap also being driven 01T by the downward thrust of the pile 30.

FIGURE 2 shows the raft 12 resting securely on a marine bottom 32 far beneath the surface 34 of the body of water. The piles 36 have been driven down through the upstanding legs or caissons 24 and into the .formations underlying the marine bottom 32. The piles 30 can each be set with an underwater pile-driving hammer as discussed in the instant inventors copending application Ser. No. 577,040, tiled Sept. 2, 1966, entitled Telescoped Caisson, or with a conventional pile-driving means while evacuating the water from a leg 24 or jacket, ahead of a pile being driven therethrough, as is taught in the instant inventors U.S. Patent No. 3,213,629 entitled Apparatus and Method for Installation of a Pile-jacket Assembly in a Marine Bottom. Furthermore, there is no difliculty in driving the piles 30 at an angle, as shown, with present machinery. After the piles 30 have been driven into the marine bottom 32 they `are temporarily fixed in the legs 24 by ballistic connections as taught in the instant inventors U.S. patent application Ser. No. 489,527, tiled Sept. 23, 1965, and entitled Ballistic Jacket-pile Connection, and then permanently secured by grouting the annulus between each pile 30 and the respective leg 24. After grouting, a shear cap 36 is placed over the upper converging ends of the support sections 14 land 16 and permanently fixed in place. A deck section 38 is mounted above the shear cap 36 `and will carry the necessary rabovesuriace equipment for the subsea system that the particular marine storage structure 1t] services. This may include gasoline or diesel engines, electric motors, final separation equipment, and possibly Veven a swivel tarangement so that the deck may be utilized as the central terminal of a single point mooring system.

Depending upon various factors not to be discussed here, the produced fluid may go through a separation stage on the marine bottom 32 in ian underwater gathering station or satellite and then be stored directly in the raft 12 or the fluid may be transported directly from the wellheads or a central gathering station up either inside or in a ilowline supported on the outside of one of the legs 4 24, to separation facilities on the deck 38, separated there, and then pumped down to the raft 12 through another leg 24 or in another flowline supported along a leg 24 for storage. The last mentioned iiuid path would also be used to transport the iiuid back to the deck 38 for offloading into a tanker. The legs 24, after the piles 30 have been driven therethrough and cemented in place, may be utilized -as fluid conduits. This can be done in several ways. One of the alternatives is to have the hinging shafts 26 and 28 of the legs 24 hollow and communieating with the interiors of at least some of the storage tubes 18A, 18B, 18E, and 181:".V This can be accomplished by having the shafts 26 and 28 open ended, and having coaxial passages extending into the interior of particular storage tubes 18 through the shaft journaling means. Remotely controlled perforating means located in the hollow shafts 26 and 28 may be utilized to form composite passages through walls of the legs 24, the grout between the piles 30 and the legs 24, and through the piles 30 into the interiors of the legs 24 to provide iuid communication with an adjacent storage tube 18. it this is not practical, a flexible pipe can be connected between the hollow interior of one or more of the storage tubes 18A-F and the hollow interior 'of a leg 24 above the grouted-in pile 30.

While in the illustrative drawings the raft 12 is shown to consist of spaced storage tubes 18A--F, this is only one of many possible configurations. For example, the raft 12 instead may be one large barge structure, preferably compartmented to aid in its controlled submergence. The legs 24 of the support sections 14 and 16 could be hinged or pivoted just above apertures through the barge and supported at their outer ends the same distance above the surface on buoys.

In some instances it may not be desirable to have the deck section 38 extend above the surface 34, but within easy diving depth therebeneath. In such cases a small deck, section may be mounted on the upper end of the support sections 14 and 16 which would converge at a point 50 to feet below the surface. For driving piles through the legs 24, when the legs 24 do not reach to the surface, temporary coaxial caissons (not shown) can be spot-welded to the upper ends of the legs 24 or an underwater hammer can be lowered into each of the legs from the surface. Relatively short unsupported flexible lines would then connect the deck section, below the surface, with a tioating station on the surface.

FIGURE 3 shows a method for erecting the storage structure 10 on the marine bottom 32 wherein at least some of the tubes 18A-F are divided into at least two axially spaced compartments. The irst step is to ood at least a portion of one end of the raft 12 until it attains a vertical attitude in the water as shown at 12A. The support sections 14 and 16 are kept buoyant by plates tack-welded over the ends of the legs 24, causing the support section 16, as shown in phantom at 16A, to oat substantially horizontally on the surface 34 of the body of water and the support section 14, as shown in phantom at 14A, to extend diagonally to the surface 34 from its articulated end which will be near the bottom 32. When this position is attained, at least a portion of the other end of the raft 12 is flooded causing the raft 12 to be submerged until it lies horizontally on the bottom 32 as shown at 12B and C. The support section 14 will be shifted laterally to the position shown in phantom at 14B, while the support section 16 will attain a mirror image of that position, shown in phantom at 16B. The support sections 14 and 16 are then pivoted inwardly until they converge, as shown at l154C and 16C, preferably with the help of tugs or derrick arges.

Although the present invention has been described in connection with details of specific embodiments thereof, it is to be understood that such details are not intended to limit the scope of the invention. The terms and expressions employed are used in a descriptive and not a limiting sense and there is no intention of excluding such equivalents, in the invention described, as fall within the scope of the claims. Now having described the apparatus and method herein disclosed, reference should be had to the claims which follow.

What is claimed is:

1. A submersible storage structure to be supported on a marine bottom and anchored in the underlying subaqueous formations comprising: a storage section and at least a pair of support sections, said storage section being a planar raft having a plurality of parallel storage tubes and means for interconnecting said storage tubes; means for pivotally connecting each of said support sections, near the inner end thereof, to said storage section, the axes of said pivotal connecting means being parallel and spaced apart; and each of said support sections being provided `with at least a pair of tubublar elongated legs spaced apart at the pivotal axis of said support section, said legs of each of said support sections being pivotally connected to said storage structure between spaced pairs of said storage tubes, said tubular legs each having an unobstructed throughbore functioning as pile guide means to permit piles to be driven therethrough from above the surface of a body of water into subaqueous formations underlying a marine bottom to anchor said storage structure when said storage structure is submerged and is supported on a marine bottom, said support sections each being of a length sufcient for the converging of the upper outer ends thereof at least near the surface of a body of water in which said storage structure is to be submerged, the upper converging ends of said support structure forming a base for mounting a deck section thereon at least within easy diving depth of the water surface.

2. A storage structure as recited in claim l wherein ones of said storage tubes adjacent and between said legs of said support sections are shorter than the over-all length of said raft comprising all of said storage tubes to permit said support sections to be unfolded into the plane of said raft whereby said storage structure floats with said support sections and said storage section on the surface of a body of water while being towed to a marine site.

3. A storage structure as recited in claim 1 wherein said means for interconnecting said storage tubes is a pair of perpendicularly intersecting tubular spacer tubes comprising tubular spacer sections between adjacent pairs of storage tubes for holding said storage tubes in a spaced parallel relationship, said storage tubes and said tubular spacer sections forming a continuous storage space with said storage tubes.

4. A storage structure supported on a marine bottom and anchored in the underlying subaqueous formations comprising: a completely submerged storage section supported on said marine bottom, said storage section being an enclosed storage area for the containment of fluids; first and second support sections; means for pivotally connecting said first support sections, at a first end, to said storage section on a first axis, means for pivotally connecting said second support section, at a rst end, to said storage section on a second axis, said first and second axes being parallel and spaced apart, said rst and second support sections extending upwardly and converging above said storage section at least near the surface of said body of water; means for connecting said converging first and second support sections to form a rigid deck section support, said first and second support sections each being provided with a pair of upwardly converging hollow legs, and piles extending from at least the lower ends of said legs and extending into the for-mations underlying said marine bottom to anchor said storage structure; and means for permanently and rigidly connecting said piles within said legs.

5. A storage structure as recited in claim 4 wherein there is a deck section mounted on said converged upper ends of said first and second support sections at least near the surface of said body of water.

6. A method for installing said storage structure of claim 4 on a marine bottom comprising the following steps:

(a) towing said storage structure to a predetermined site with said storage and said rst and second support sections oating on said surface of said body of water;

(b) flooding one end of said storage section, which is is compartmented, until said storage section is substantially vertical in the water with the flooded end resting on said marine bottom, said first of said support sections being positioned with at least the second free end thereof floating on the surface of said body of water, and said second of said support sections extending toward said surface from the respective pivotal connection to said storage section;

(c) completely ooding said storage section whereby said storage section will substantially pivot on said end already resting on said marine bottom until the entire storage section is supported on said marine bottom, said first and second support sections both extending toward said surface of said body of water from their respective pivotal connections;

(d) moving the upper free ends of said first and second support sections together above said storage section, at least near said surface of said body of water;

(e) fastening said upper converging ends of said first and second support sections rigidly together;

(f) driving piles into said subaqueous formations underlying said marine bottom from above the surface of said body of water through said tubular legs of said first and second support structure; and

(g) permanently rigidly fastening said piles in said legs after driving said piles to anchor said storage structure.

7. A method for installing said storage structure of claim 6 comprising the following additional step:

(h) mounting a deck section at least near said surface of said body of water on a rigid support formed by the upper ends of said first and second support sections.

References Cited UNITED STATES PATENTS 2,589,146 3/1952 Samuelson 61-465 2,968,930 l/l96l Mangone 6l-46.5 3,306,052 2/1967 Kawasaki 61--465 ACOB SHAPIRO, Prima/y Examiner.

D. J. WILLIAMOWSKY, Examiner. 

